Confusion Over Organization of Images in Lightroom

Re question 2, when you import the files change the option to "add"  at the top of the import window. Lightroom will then see the folder you created  in windows file explorer. If  it is set to move or copy, the destination panel on right side of window will have drop down which allows you to put all  imported files in one folder or seperate folders by date.

There are lots of ways to add images to Collections. [edit: I won't repeat what is already covered]

All of the folders of your C: drive are not listed in the Folders panel, because that is not what it is about, and not what it is for. The Catalog is a database holding entries for lots of imported images. Each entry holds your edits etc, also an address of where the source file is located. The Folders panel reports and summarises all of the addresses information that the Catalog holds. Any folder, and any file, that the Catalog does not hold any prior record of - will therefore not show.

But those it does hold a record of, are thereby able to participate in all sorts of clever stuff. We gain value back from the selectivity, and also from the extra organisational effort, invested in an import procedure.

Analogy: two copies of the same book on a table. One has just come out of someone's pocket, the other is part of a library's collection and has just come off the shelf. They are both physically inside the library building. The first is a book. The second is a library book.

Another option is to create a new collection and temporarily designate it as the target collection. Then, any image that you mark with the little circle in the filmstrip (upper right hand corner) will automatically be added to that collection. After you have completed adding images to the collection you can change the target collection back to the quick collection or to some other collection if you choose to do so.

1. You can also select all the images that you want to place into a specific collection, then right-click on that collection and click on "Add Selected Photos to this Collection".

2. What @dj_paige said. 

1. You can drag and drop the photos onto the collection name. Or you can right-click on the collection name and select "Set as Target Collection" and then selecting the photo and pressing B (or clicking on the Quick Collection icon) will add the photos to this collection (not the Quick Collection).

2. Lightroom Classic is not a file browser like Windows Explorer or Mac Finder. It is a database. It doesn't know anything about folders you create in your operating system. It only knows about the folder(s) where photos in its database are stored. Generally, there's no need to create an operating system folder to "place together" photos that you think should be together. This should all be done via keywords, or metadata or collections. Lightroom Classic gives you these tools within its interface so that you don't have to go outside of Lightroom Classic (to your operating system or to other software) to keep photos organized.

I'm trying to accomplish the same thing with both of these questions -- isolating some of my images so that they're not jump lumped in with the rest and therefore easier to find (even if I don't remember the date they were taken).

All of your photos that have been imported into Lightroom Classic will appear in the "All Photographs" view in the Library Module. You can "isolate" them by keywords, metadata or collections, but they will always be in "All Photographs" and you can't turn this off. But if they have a keywords or metadata or are in a collection, they are easier to find.